scholarly journals Herbig–Haro flows around the BBWo 192E (GM 1–23) nebula

2020 ◽  
Vol 498 (4) ◽  
pp. 5109-5115
Author(s):  
T Yu Magakian ◽  
T A Movsessian ◽  
H R Andreasyan ◽  
J Bally ◽  
A S Rastorguev
Keyword(s):  
Star Formation ◽  
Sloan Digital Sky Survey ◽  
Young Stellar Objects ◽  
Infrared Range ◽  
Wide Field ◽  
Proper Motions ◽  
Dark Cloud ◽  
Stellar Objects ◽  
Reflection Nebula ◽  
Sky Survey

ABSTRACT Looking for evidence of recent star formation, we have studied a small comet-shaped reflection nebula, known as BBWo 192E (GM 1–23), which is located in the dark cloud SL 4 in the Vela Molecular Ridge cloud C, and a young infrared cluster embedded into the nebula. We obtained the images of BBWo 192E in Hα and [S ii] lines and in a Sloan Digital Sky Survey i ′ filter with the Blanco telescope at the Cerro Tololo Inter-American Observatory in order to discover new Herbig–Haro (HH) flows. We used the Two-Micron All-Sky Survey and the Wide-field Infrared Survey Explorer to search for additional member stars of the cluster. We also studied the proper motions and parallaxes of the cluster members using GAIA Data Release 2. Five new groups containing at least nine HH objects, tracing several distinct outflows, were revealed. A previously unreported reflection nebula and a number of probable outflow sources were found in the infrared range. The proper motions allowed us to select eight probable member stars in the visual range. Their parallaxes correspond to a mean distance 800 ± 100 pc for this cluster. The bolometric luminosities of the brightest cluster members are 1010 L⊙ (IRAS 08513−4201, the strong source in the centre of the cluster) and 2–6 L⊙ for the five other stars. The existence of optical HH flows around the infrared cluster of young stellar objects suggests that star formation in this cloud is ongoing around the more massive Herbig Ae/Be star. Considering its morphology and other features, this star-forming region is similar to the zone of star formation near CPM 19.

scholarly journals Sequential star formation in the filamentary structures of the Planck Galactic cold clump G181.84+0.31

2019 ◽  
Vol 487 (1) ◽  
pp. 1315-1334 ◽  
Author(s):  
Lixia Yuan ◽  
Ming Zhu ◽  
Tie Liu ◽  
Jinghua Yuan ◽  
Yuefang Wu ◽  
...  
Keyword(s):  
Star Formation ◽  
Unit Length ◽  
Line Emission ◽  
Young Stellar Objects ◽  
Wide Field ◽  
Stellar Objects ◽  
Filamentary Structure ◽  
Dense Cores ◽  
Velocity Gradients ◽  
Sky Survey

Abstract We present a multiwavelength study of the Planck Galactic cold clump G181.84+0.31, which is located at the northern end of the extended filamentary structure S242. We have extracted nine compact dense cores from the SCUBA-2 850-$\hbox{$\mu $m}$ map, and we have identified 18 young stellar objects (YSOs; four Class I and 14 Class II) based on their Spitzer, Wide-field Infrared Survey Explorer(WISE) and Two-Micron All-Sky Survey (2MASS) near- and mid-infrared colours. The dense cores and YSOs are mainly distributed along the filamentary structures of G181.84 and are well traced by HCO+(1–0) and N2H+(1–0) spectral-line emission. We find signatures of sequential star formation activities in G181.84: dense cores and YSOs located in the northern and southern substructures are younger than those in the central region. We also detect global velocity gradients of about 0.8 ± 0.05 and 1.0 ± 0.05 km s−1 pc−1 along the northern and southern substructures, respectively, and local velocity gradients of 1.2 ± 0.1 km s−1 pc−1 in the central substructure. These results might be due to the fact that the global collapse of the extended filamentary structure S242 is driven by an edge effect, for which the filament edges collapse first and then further trigger star formation activities inward. We identify three substructures in G181.84 and estimate their critical masses per unit length, which are ∼101 ± 15, 56 ± 8 and 28 ± 4 M⊙ pc−1, respectively. These values are all lower than the observed values (∼200 M⊙ pc−1), suggesting that these substructures are gravitationally unstable.

SiO as a chemical signature of outflows from bright, compact sources in MSX IR-dark clouds

2004 ◽  
Vol 82 (6) ◽  
pp. 740-743 ◽  
Author(s):  
P A Feldman ◽  
R O Redman ◽  
L W Avery ◽  
J Di Francesco ◽  
J D Fiege ◽  
...  
Keyword(s):  
Star Formation ◽  
Young Stellar Objects ◽  
Line Profiles ◽  
Bipolar Outflows ◽  
Dark Cloud ◽  
Stellar Objects ◽  
Dark Clouds ◽  
Dense Cores ◽  
Infrared Dark Clouds ◽  
Compact Sources

The line profiles of dense cores in infrared-dark clouds indicate the presence of young stellar objects (YSOs), but the youth of the YSOs and the large distances to the clouds make it difficult to distinguish the outflows that normally accompany star formation from turbulence within the cloud. We report here the first unambiguous identification of a bipolar outflow from a young stellar object (YSO) in an infrared-dark cloud, using observations of SiO to distinguish the relatively small amounts of gas in the outflow from the rest of the ambient cloud. Key words: infrared-dark clouds, star formation, bipolar outflows, SiO, G81.56+0.10.

scholarly journals Fundamental differences in the radio properties of red and blue quasars: insight from the LOFAR Two-metre Sky Survey (LoTSS)

2020 ◽  
Vol 494 (3) ◽  
pp. 3061-3079 ◽  
Author(s):  
D J Rosario ◽  
V A Fawcett ◽  
L Klindt ◽  
D M Alexander ◽  
L K Morabito ◽  
...  
Keyword(s):  
Star Formation ◽  
Control Sample ◽  
Low Frequency ◽  
Galactic Nuclei ◽  
Sloan Digital Sky Survey ◽  
Stellar Objects ◽  
Radio Detection ◽  
Sky Survey ◽  
Quasi Stellar Objects ◽  
First Time

ABSTRACT Red quasi-stellar objects (QSOs) are a subset of the luminous end of the cosmic population of active galactic nuclei (AGNs), most of which are reddened by intervening dust along the line of sight towards their central engines. In recent work from our team, we developed a systematic technique to select red QSOs from the Sloan Digital Sky Survey, and demonstrated that they have distinctive radio properties using the Faint Images of the Radio Sky at Twenty centimetres radio survey. Here we expand our study using low-frequency radio data from the LOFAR Two-metre Sky Survey (LoTSS). With the improvement in depth that LoTSS offers, we confirm key results: Compared to a control sample of normal ‘blue’ QSOs matched in redshift and accretion power, red QSOs have a higher radio detection rate and a higher incidence of compact radio morphologies. For the first time, we also demonstrate that these differences arise primarily in sources of intermediate radio loudness: Radio-intermediate red QSOs are × 3 more common than typical QSOs, but the excess diminishes among the most radio-loud systems and the most radio-quiet systems in our study. We develop Monte Carlo simulations to explore whether differences in star formation could explain these results, and conclude that, while star formation is an important source of low-frequency emission among radio-quiet QSOs, a population of AGN-driven compact radio sources is the most likely cause for the distinct low-frequency radio properties of red QSOs. Our study substantiates the conclusion that fundamental differences must exist between the red and normal blue QSO populations.

scholarly journals Molecular environs and triggered star formation around the large Galactic infrared bubble N 24

2019 ◽  
Vol 487 (2) ◽  
pp. 1517-1528 ◽  
Author(s):  
Xu Li ◽  
Jarken Esimbek ◽  
Jianjun Zhou ◽  
W A Baan ◽  
Weiguang Ji ◽  
...  
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Young Stellar Objects ◽  
Collapse Mechanism ◽  
Kinetic Temperature ◽  
H Ii Regions ◽  
Dark Cloud ◽  
Stellar Objects ◽  
Multi Wavelength ◽  
Mass Size

Abstract A multi-wavelength analysis of the large Galactic infrared bubble N 24 is presented in this paper in order to investigate the molecular and star-formation environment around expanding H ii regions. Using archival data from Herschel and ATLASGAL, the distribution and physical properties of the dust over the entire bubble are studied. Using the Clumpfind2d algorithm, 23 dense clumps are identified, with sizes and masses in the range 0.65–1.73 pc and 600–16 300 M⊙, respectively. To analyse the molecular environment in N 24, observations of NH3 (1,1) and (2,2) were carried out using the Nanshan 26-m radio telescope. Analysis of the kinetic temperature and gravitational stability of these clumps suggests gravitational collapse in several of them. The mass–size distributions of the clumps and the presence of massive young protostars indicate that the shell of N 24 is a region of ongoing massive-star formation. The compatibility of the dynamical and fragmentation timescales and the overabundance of young stellar objects and clumps on the rim suggest that the ‘collect-and-collapse’ mechanism is in play at the boundary of the bubble, but the existence of the infrared dark cloud at the edge of bubble indicates that a ‘radiation-driven implosion’ mechanism may also have played a role there.

scholarly journals SK 1: A possible case of triggered star formation in perseus

2006 ◽  
Vol 2 (S237) ◽  
pp. 217-221
Author(s):  
Miriam Rengel ◽  
Klaus Hodapp ◽  
Jochen Eislöffel
Keyword(s):  
Star Formation ◽  
Molecular Clouds ◽  
Thermal Emission ◽  
Young Stellar Objects ◽  
Wide Field ◽  
Dust Shell ◽  
Stellar Objects ◽  
Star Forming ◽  
Star Forming Regions ◽  
Suitable Target

AbstractAccording to a triggered star formation scenario (e.g. Martin-Pintado & Cernicharo 1987) outflows powered by young stellar objects shape the molecular clouds, can dig cavities, and trigger new star formation. NGC 1333 is an active site of low- and intermediate star formation in Perseus and is a suggested site of self-regulated star formation (Norman & Silk 1980). Therefore it is a suitable target for a study of triggered star formation (e.g. Sandell & Knee 2001, SK1). On the other hand, continuum sub-mm observations of star forming regions can detect dust thermal emission of embedded sources (which drive outflows), and further detailed structures.Within the framework of our wide-field mapping of star formation regions in the Perseus and Orion molecular clouds using SCUBA at 850 and 450 μm, we mapped NCG 1333 with an area of around 14′× 21′. The maps show more structure than the previous maps of the region observed in sub-mm. We have unveiled the known embedded SK 1 source (in the dust shell of the SSV 13 ridge) and detailed structure of the region, among some other young protostars.In agreement with the SK 1 observations, our map of the region shows lumpy filaments and shells/cavities that seem to be created by outflows. The measured mass of SK 1 (~0.07 M) is much less than its virial mass (~0.2-1 M). Our observations support the idea of SK 1 as an event triggered by outflow-driven shells in NGC 1333 (induced by an increase in gas pressure and density due to radiation pressure from the stellar winds that have presumably created the dust shell). This kind of evidences provides a more thorough understanding of the star formation regulation processes.

scholarly journals Triggered star formation in the isolated cluster CB 34?

2006 ◽  
Vol 2 (S237) ◽  
pp. 464-464
Author(s):  
Dawn E. Peterson ◽  
R. A. Gutermuth ◽  
M. F. Skrutskie ◽  
S. T. Megeath ◽  
J. L. Pipher ◽  
...  
Keyword(s):  
Star Formation ◽  
Class Ii ◽  
High Rate ◽  
Young Stellar Objects ◽  
Collapse Mechanism ◽  
Stellar Objects ◽  
Hii Region ◽  
Dark Clouds ◽  
Sky Survey ◽  
Bok Globules

AbstractBok globules, optically opaque small dark clouds, are classical examples of isolated star formation. However, the collapse mechanism for these cold, dense clouds of gas and dust is not well understood. Observations of Bok globules include some which appear to be starless while others harbor single stars, binaries and even small groups of forming stars. One example of a Bok globule forming a group of stars is CB 34, observed with both the IRAC and MIPS instruments as part of the Spitzer Young Cluster Survey. Based on initial analysis of 1-8 μm photometry from IRAC and the Two Micron All Sky Survey (2MASS), we identified 9 Class 0/I and 14 Class II young stellar objects within the small, 4.5′ × 4.5′ region encompassing CB 34. This unusually high number of protostars compared with Class II sources is intriguing because it implies a high rate of star formation. Therefore we have begun a larger study of this region in order to determine why and how CB 34 started forming stars at such a high rate. Is CB 34 embedded within a larger HII region which may have triggered its collapse or does it appear to have collapsed in isolation from outside influences?

scholarly journals Triggered star formation in a cometary atomic/molecular cloud in the Cep OB3 association

2019 ◽  
Vol 489 (4) ◽  
pp. 4809-4816 ◽  
Author(s):  
Brandon Marshall ◽  
C R Kerton
Keyword(s):  
Star Formation ◽  
Galactic Plane ◽  
Initial Conditions ◽  
Young Stellar Objects ◽  
Wide Field ◽  
Infrared Source ◽  
Stellar Objects ◽  
Iras Source ◽  
Infrared Observations ◽  
Infrared Survey

ABSTRACT We present a study of a small atomic/molecular cometary cloud associated with the infrared source IRAS 23153+6938. The cloud is located 70 pc from the massive O-type stars in the Cepheus OB3 association, and is very likely an excellent example of triggered star formation via radiation-driven implosion (RDI). The cloud was studied using $\rm{H\,\small{I}}$ and 12CO data from the Canadian Galactic Plane Survey (CGPS) and infrared observations from the Wide-field Infrared Survey Explorer (WISE) telescope. The molecular mass is approximately MH2 = 350 ± 45 M$\odot$, and we find that the single IRAS source is actually the centre of a small cluster of class I and class II young stellar objects (YSOs). To compare with theory, we make reasonable estimates for the cometary cloud’s initial conditions and find that the cloud is located within the correct theoretical phase space for RDI to occur. In addition, both the morphology of the cloud and the location of different YSO classes relative to the cloud match what would be expected for RDI. We conclude that RDI is the most likely explanation for star formation within the cloud, and we suggest that similar studies of molecular clouds associated with nearby OB associations may be able to identify comparable examples.

scholarly journals Compact planetary nebulae: improved IR diagnostic criteria based on classification tree modelling

2019 ◽  
Vol 488 (3) ◽  
pp. 3238-3250 ◽  
Author(s):  
Stavros Akras ◽  
Lizette Guzman-Ramirez ◽  
Denise R Gonçalves
Keyword(s):  
Classification Tree ◽  
Planetary Nebulae ◽  
Young Stellar Objects ◽  
H Ii Regions ◽  
Wide Field ◽  
Stellar Objects ◽  
Isaac Newton ◽  
Sky Survey ◽  
Machine Learning Approach ◽  
Tree Models

Abstract Planetary nebulae (PNe) are strong H α line emitters and a lot of new PNe discoveries have been made by the SuperCOSMOS AAO/UKST H α Survey (SHS) and the Isaac Newton Telescope Photometric H α Survey (IPHAS). However, their resulting list of candidates turned out to be heavily contaminated from H α-line mimics like young stellar objects (YSOs) and/or H ii regions. The aim of this work is to find new infrared criteria that can better distinguish compact PNe from their mimics using a machine learning approach and the photometric data from the Two-Micron All-Sky Survey and Wide-field Infrared Survey Explorer. Three classification tree models have been developed with the following colour criteria: W1 − W4 ≥ 7.87 and J − H < 1.10; H − W2 ≥ 2.24 and J − H < 0.50; and Ks− W3 ≥ 6.42 and J − H < 1.31 providing a list of candidates, characterized by a high probability to be genuine PNe. The contamination of this list of candidates from H α mimics is low but not negligible. By applying these criteria to the IPHAS list of PN candidates and the entire IPHAS and VPHAS+ DR2 catalogues, we find 141 sources, from which 92 are known PNe, 39 are new very likely compact PNe (without an available classification or uncertain) and 10 are classified as H ii regions, Wolf–Rayet stars, AeBe stars, and YSOs. The occurrence of false-positive identifications in this technique is between 10 and 15 per cent.

The CepHeus-A Star formation and proper Motions (CHASM) Survey

2017 ◽  
Vol 13 (S336) ◽  
pp. 231-234
Author(s):  
Alberto Sanna
Keyword(s):  
Star Formation ◽  
Young Star ◽  
Young Stellar Objects ◽  
Proper Motions ◽  
Stellar Objects ◽  
Very Large Array ◽  
Star Forming ◽  
Long Baseline ◽  
T Tauri ◽  
Cepheus A

AbstractThe “CepHeus-A Star formation and proper Motions” (CHASM) survey is a large project consisting of a combination of astrometric Very Long Baseline Array (VLBA) and Jansky Very Large Array (VLA) observations, to map both the stellar and dense molecular gas components in the star-forming region Cepheus A. With the VLBA, we make use of the CH3OH and H2O maser emission in the vicinity of Cepheus A HW2, in order to measure accurate proper motions and parallax distances to both T Tauri stars and massive young stellar objects (YSOs) belonging to the same star-forming region. With the Jansky VLA, we make use of the interstellar thermometer NH3, in order to image the molecular clump surrounding Cepheus A HW2 and to determine its physical conditions. By combining these informations all together, we can provide, for instance, a direct measurement of the Bondi-Hoyle accretion radius for a massive young star, namely, HW2.

scholarly journals Triggered cluster formation in the RMC

2006 ◽  
Vol 2 (S237) ◽  
pp. 439-439
Author(s):  
Jin Zeng Li ◽  
Michael D. Smith
Keyword(s):  
Star Formation ◽  
Molecular Complex ◽  
Cluster Formation ◽  
Young Stellar Objects ◽  
The South ◽  
Stellar Objects ◽  
Hii Region ◽  
Main Cluster ◽  
Sky Survey ◽  
Rosette Nebula

AbstractA comprehensive study of clustered star formation in the Rosette Molecular Complex was carried out based on archived data from the 2 Micron All Sky Survey. We presented strong evidence that triggered formation of embedded clusters and stellar aggregates took place in the working shells of the Rosette Nebula, a spectacular HII region excavated by the dozens of OB stars of the emerging massive cluster NGC 2244. Surprisingly, we have identified, within the confines of NGC 2244, a distinct congregation of young stellar objects showing prominent NIR excess that forms an arc like structure in appearance. Its location right to the south-east of the center of the main cluster and its strange morphology indicate most likely an origin from a former working shell of the HII region. This relic arc and the large, fragmented working surface layer of Rosette with the ambient cloud roughly show a concentric origin in morphology. This implies also a common origin of the clusters or stellar aggregates in association. The formation of massive star clusters was evidenced further into the heart of the molecular complex, and structured clustering star formation seemed to have taken place toward the south-east edge of the complex.

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